The Role of Food Web Models in the Environmental Management of Bioaccumulative Chemicals

Abstract

When properly calibrated, food web models can be used to estimate the tissue concentrations of bioaccumulative chemicals in aquatic organisms at various trophic levels. In general, such models are dependent on the knowledge of the bioenergetics and feeding interactions within a food web and the sediment and water concentrations of chemicals. The results of a preliminary probabilistic model that was constructed for a food web of the tidal Passaic River in New Jersey are presented. The basis for constructing and calibrating the model was to supplement available tissue-residue data for risk assessment and to evaluate future trends of bioaccumulation and potential risk under hypothetical scenarios regarding future conditions in the Passaic River. Following the construction and preliminary runs of the model, tissue-residue data were collected to evaluate the performance of the model. The comparison of the estimated and measured concentrations of select coplanar polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-di-oxins and dibenzofurans (PCDDs/Fs) suggested that the model performed well for the site. The mean estimated concentrations of these chemicals were generally within an order of magnitude or less of the mean measured concentrations in mummichog (Fundulus heteroclitis), blue crab (Callinectes sapidus), and the edible portions of striped bass (Morone saxatilis). The utility of models is their ability to help evaluate events beyond the bounds of the available tissue-residue data, including future bioaccumulation potential within the food web under new or altered conditions. Under regulatory programs such as Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and the Resource Conservation and Recovery Act, once remedial objectives are established, a food web model can be used to help develop ranges of clean-up goals that may be necessary to achieve the regulatory objectives for bioaccumulative chemicals.